1. Field of the Invention
The present invention generally relates to a method and apparatus for transferring information, and more particularly, to a method and apparatus for transferring information which will efficiently download the same information, for example, software, to a plurality of offices constructing a network.
The present invention is also directed to a method and apparatus for transferring information which downloads special information to a given office.
2. Description of the Related Art
A telecommunication network becomes complex in order to provide a variety of services. Therefore, it becomes important to manage such a network. Network management is currently developed also in international standardization. For example, in the international telecommunication union (ITU-T), standardization of an operation of a telecommunication carrier and a telecommunication management network (TMN) for network management is carried out. Also, supervision and control of the telecommunication is standardized.
For such network management, respective transmission equipment in offices constructing the network has a managing function, and the transmission equipment in the offices is managed by a given operation center. In general, each office's managing function is constructed with software. When the network is initially constructed, or when the managing function is added and changed, it is necessary to install new software of the managing function to the transmission equipment of the respective offices.
In the prior art, for changing the software of the transmission equipment in a remote office, a maintenance man changes a ROM of the equipment in the remote office. However, for developing the above-mentioned management network, a software download technique, namely a technique loading or updating the software of the remote office by using a communication line, is now indispensable.
At present, several download methods for a network managing system are known. In a typical method, a server office sequentially downloads the software to a plurality of offices on the network in a relay transmission form. FIG. 1 shows an illustration for explaining that prior-art downloading method. FIG. 1 shows a linear-structure network model in which offices A to F are connected in series. In the prior-art downloading method, the office A downloads the information to respective offices, or the office A initially downloads to the adjacent office B, next, the office B downloads to the adjacent office C, and at last, the office E downloads to the office F.
However, in the above-mentioned prior-art method, there is the following problem. A download time increases in proportion to a number of offices in the network. For example, when the download time for one office is 10 minutes, it takes 1000 minutes for downloading of 100 offices. This method is represented by an O(n) method in which a total download time for n offices is n times the download time for one office.
In an ideal downloading method, it is known that the total download time for n offices is approximately log.sub.2 n times the download time for one office. For example, when the download time for one office is 10 minutes, it takes approximately 70 (10.times.log.sub.2 100) minutes for downloading of 100 offices. This method is represented by an O(log.sub.2 n) method.
For realizing the ideal downloading method, another method is proposed in a reference "SEMF software architecture for SDH transmission equipment", Japanese technical report of the Institute of Electronics, Information and Communication engineers (IEICE), IN93-41 (1993-08), pp.41-46. In this method, the download of the O(log.sub.2 n) method may be carried out only in a limited network model.
FIG. 2 shows an illustration for explaining the prior-art downloading method disclosed in the above-mentioned reference. There are two models, a model A indicates a network model in which all offices are connected with each other by lines, and a model B indicates a network model in which all offices are connected in series (linear structure) by the lines. In this method, when the software is downloaded to any office, this office operates as a server, and downloads to an adjacent office. The download is carried out in an undefined order. Therefore, this method is applicable to the model A, but is not applicable to the model B.
When the method disclosed in the above-mentioned reference is applied to the model A, the software can be downloaded to all offices by 3-downloading operations. For example, after the downloading operation from the office A to the office B is carried out (t1), the downloading operation from the office A to the office E and the downloading operation from the office B to the office C can simultaneously be carried out (t2). Therefore, the download may be performed by the O(log.sub.2 n) method.
However, to the model B in FIG. 2, the method in the above-mentioned reference can not be applied. In the model B, after the downloading operation from the office A to the office B is carried out (t1), the downloading operation from the office A to the office E and the downloading operation from the office B to the office C cannot simultaneously be carried out because of traffic overlapping in network lines. Therefore, for downloading of all offices, 4-downloading operations are required. In the model B, the download cannot be performed by the O(log.sub.2 n) method.
As discussed above, the prior-art downloading method in the above-mentioned reference is applicable to only a case where all offices are connected with each other by the lines, and a case where a network model is identical to a model supporting the O(log.sub.2 n) method. Therefore, in the prior-art downloading method, there is a problem in that the download time increases. When the download time increases, the time for the maintenance man waiting for the downloading also increases, and, thus, network-management efficiency is degraded.